Calcium Magnesium Nitrate — Frequently Asked Questions

Because they compete for uptake. Both are taken up through the same root transport pathways, so an excess of one suppresses absorption of the other. A grower correcting a calcium deficiency with calcium nitrate alone can induce a magnesium deficiency in the process. A double salt holds the ratio between them constant through the season and removes that risk.

It varies by product and should be stated on the specification rather than assumed, since different crops and growing systems call for different balances. What matters is that the ratio is fixed and known, so a nutrient programme can be built around it and the antagonism between the two cations is managed rather than accidental.

Because nitrate uptake at the root actively drives cation uptake alongside it, while ammonium competes with calcium and magnesium for the same pathway. Using nitrate as the nitrogen carrier therefore supports absorption of both nutrients, whereas an ammonium or urea-based product would work against it.

Through fertigation, hydroponic nutrient solutions or as a foliar feed, since it is fully water-soluble. It is hygroscopic and must be stored sealed and dry. Compatibility should be checked before tank mixing, since calcium will precipitate with sulphate and phosphate sources if they are combined in concentrated stock solutions.